Certain evergreen trees like the Douglas fir and the Australian pine can form extensive root systems when grown in optimal conditions. The main root can go as far down as a taproot and even keep going down until there is not enough oxygen to support further growth. But is this the case for all evergreens?
Not all evergreens have deep roots, but the average length is 132.3 inches (336 cm). Most of these trees have anchoring roots, but the majority of their root system stays within a depth of 12 to 15 inches (30 to 40 cm). Soil type also influences the depth of evergreen root systems.
This article delves into the root systems in evergreen trees and how they contribute to the trees’ health and resistance to disease. We’ll also discuss the diseases that affect these evergreens’ roots and how to prevent them.
How Evergreen Tree Roots Spread
Evergreen tree roots usually spread until they reach the circumference of the canopy. Even when they spread beyond the furthest canopy point, it’s only by a few feet. That’s why the roots pose no risk to property such as the foundation of your house.
However, most evergreens with shallow roots are at risk of hazards:
- High winds: High winds can uproot a tree by tilting it or tipping it over.
- Damp soil: Damp soil loosens the roots, causing the tree to lose grip.
- Driveways or paved paths: These can obstruct root development.
Leaving enough space between trees is essential when creating an evergreen garden. This will enable the trees to develop a healthy root system. Spacing will also allow the canopy to spread to its maximum circumference.
Plant your evergreens as far apart as the dripline of the mature tree can extend. For example, if you’re planting Emerald Greens, leave a 3 to 4 feet (.91 to 1.22 m) space between each tree because that will be their approximate canopy circumference at maturity.
Here is a list of short-rooted and long-rooted evergreens:
| Evergreens With Long Roots | Evergreens With Short Roots |
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Direction of the Roots
Generally, the roots of an evergreen tree are much wider than they are deep:
Downward Root Growth
The roots of most evergreen trees grow outward rather than downward. Since their root system is relatively shallow, their deepest penetration below the surface is approximately 2 feet (61 cm).
Sideways Root Growth
An evergreen’s roots can spread as wide as the widest portion of the canopy. One of the notable features of fibrous root systems is their horizontal growth. As a rule, fibrous roots are also fragile—although they can spread fairly widely, they pose little to no danger to your home’s foundation or other fixtures.
Soil Properties Affecting Root Systems in Evergreens
The type of soil around an evergreen tree will play a role in how deep its roots can go.
Here are the main factors:
- Moisture: Prolonged exposure to waterlogged soil, which lacks enough oxygen, causes root rot and eventual root death.
- Aeration: Evergreen root systems like soils with a minimum of 15% oxygen level.
- Fertility: Evergreens develop robust, deeper, and better-branched roots in fertile soils, but they may grow slender and poorly branched roots in infertile soil.
- Particle size: Silty soil supports extensive and deeper root systems. On the other clay soil retains moisture for extended periods, reducing the roots’ need to spread further in search of water.
Root Diseases Affecting Evergreens
Evergreen root diseases result from soil-borne fungal growth.
These are some of the most common fungi that cause disease in evergreens:
- Phytophthora
- Pythium
- Rhizoctonia
- Fusarium
- Thielaviopsis
These pathogens arise from improper mulching, excessive irrigation, and collar, root, and crown rots. This harmful soil-borne fungus can survive for years in relatively damp soil if you don’t take proper preventive measures on time, but it can’t spread without moisture. To stop an infestation, create a reliable drainage and water management system.
How Diseases Spread
The roots of most evergreens are most vulnerable to diseases caused by fungi that attack smaller non-woody roots, such as Phytophthora and Annosus. You can only identify the condition through lab testing; however, yellowing of the leaves and tip death are two of phytophthora’s main symptoms. It is worse in locations with inadequate drainage.
Annosus root rot begins with the fungus developing on evergreen stumps. The disease spreads through the stump’s roots touching the roots of other trees. The newly infected large roots die, and eventually, the tree dies.
The initial symptoms include yellowing roots, which can advance to brown or reddish-brown leaves. The damaged tree’s roots may develop a fungus that produces tiny, unusual brown and white fruiting buds. This disease has no known treatment.
Symptoms Seen in Evergreens
You can diagnose root rot disease on your trees by examining the roots and the surrounding soil.
Here are a few signs of evergreen fungal infestation:
- Mush-covered roots
- Blackening root system
- Swamp-smelling root ball
Apart from these root symptoms, the tree can exhibit signs of disease above the ground on the leaves and tree trunk.
For example, Phytophthora and Annosus cause the leaves to turn from green to yellow and orange. The discoloration starts at the center of the tree and spreads outwards.
At first, this might not seem like an infestation at all. The disease can evolve to the point that half of the tree becomes yellow, but the infected leaves don’t fall off for a while.
The bottom line is that root disease symptoms don’t only appear in the roots but can affect any other part of the tree.
How to Prevent Root Rot
As we mentioned earlier, overwatering evergreens will render the soil soggy. The water will fill the soil’s waterways. This subjects the tree to oxygen starvation, which can kill the tree if left unchecked.
Moreover, waterlogging creates an environment that conduces to root rot, which is the main disease you should prevent in evergreens.
To prevent root rot, here are some of the strategies you can implement on your tree farm:
Water Sparingly
Wait until the soil around the roots is drained before watering the evergreen again. You can take some soil in your hand and sift it in your palm to check its wetness. If it’s dry, it should be irrigated twice a week.
Mulch Properly
Water can evaporate quickly during especially dry periods. You can reduce evaporation by covering the soil with 2-4 inches (5-10 cm) of mulching material. Mulching your evergreen also means you won’t have to water it as often.
Apply Liquid Fungicide
Treat and control evergreen root rot diseases with the right fungicides, such as Dow AgroSciences Eagle 20EW (available on Amazon.com). This liquid fungicide is known for preventing and controlling up to 15 types of evergreen and lawn fungal diseases. Carefully follow the instructions provided by the fungicide.
Dig Trenches
Dig trenches between diseased root systems and healthy ones to stop the spread of the infection. Keep in mind that if over half the root system has been compromised, the tree won’t recover.
Introduce Beneficial Microorganisms
Predatorial soil fungus and bacteria feed on the organic content in the soil, promote plant growth, and shield the roots from organisms that cause disease. Compost manure, garden compost, and organic soil conditioners are all good options for organic matter.
Final Thoughts
Some evergreens have short roots, while others develop larger networks. However, the depth and robustness of an evergreen tree’s root system depend on the soil profile and drainage.
To boost root development in evergreens, make sure the roots have access to all the nutrients they need.
Finally, check for symptoms of evergreen root disease regularly. If you suspect an infection, use the appropriate fungicide to treat the tree and prevent the spread of the disease.
